He Owns Much of Ethiopia. The Saudis Won’t Say Where They’re Keeping Him.

He supplies coffee to Starbucks. He owns much of Ethiopia. And he is known as “Sheikh Mo” in the Clintons’ circle.

But the gilded life of Sheikh Mohammed Hussein Al Amoudi took a sharp turn in November. Mr. Amoudi, the gregarious 71-year-old son of a Yemeni businessman and his Ethiopian wife, was swept up with hundreds of billionaires, princes and other well-connected figures in what the Saudi government says is an anti-corruption campaign that has seized more than $100 billion in assets.

Many other detainees, who were initially kept at a Ritz-Carlton hotel in Riyadh, have been released, including Prince Alwaleed bin Talal, the well-known international investor. Mr. Amoudi’s cousin, Mohammed Aboud Al Amoudi, a property developer, was also let go.

But Mr. Amoudi, once called the world’s richest black person by Forbes, has not been freed, leaving a vast empire that employs more than 70,000 people in limbo. He controls businesses from Ethiopia, where he is the largest private employer and the most prominent backer of the authoritarian government, to Sweden, where he owns a large fuel company, to London, which he has used as a base to set up a number of companies.

“He was in the Ritz-Carlton but we have been told by his family members that he was moved, along with others, to another hotel,” Mr. Amoudi’s press office said in an email responding to questions. “Unfortunately we do not know where. He is in regular contact with his family and is being treated well.”

While Mr. Amoudi lacks a princely pedigree, he is in other ways an archetype of those entangled in the kingdom’s power play: a billionaire with assets stretching across the world who had close ties to previous governments.

The late King Abdullah was a supporter of Mr. Amoudi’s Saudi Star Agricultural Development, a sprawling farming venture in Ethiopia established to supply rice to Saudi Arabia. Such ventures are seen as strategic assets in a desert kingdom keenly aware of its agricultural limitations. While Saudi Star has had a tough time getting going, it is said to be a particular focus of the new government’s interest.

Saudi officials have declined to comment on the charges against individual detainees as well as their status, citing privacy laws.